California has been driving America’s clean energy transition for years, but the road to net-zero is still paved with fossil fuels. Frequent extreme weather events and surging electricity demand are catalyzing the buildout of more reliable and secure clean energy. The state’s shift has largely been focused on renewable sources like solar and wind, which comprised a third of California’s average energy supply in 2021. Baseload sources of natural gas and nuclear have filled in the energy system’s intermittency gaps. Now, with California’s last nuclear power plant on the brink of closure, the state’s energy future rests on the judgment of the U.S. Nuclear Regulatory Commission (NRC)—and we can’t afford any missteps.

Decommissioning Diablo Canyon

The Diablo Canyon Power Plant (DCPP), a two-reactor facility located on the central coast of California, produces nearly 10% of the state’s total energy. Despite its role in the state’s power portfolio, decisions were made to sunset DCPP when the operating licenses for its reactors expire in 2024 and 2025.

But carving DCPP from California’s grid is not as simple as it seems. Not only would the state lose thousands of megawatts of reliable, carbon-free power, but California needs to spend $30 billion on long-lead transmission development to support the new generation necessary to reach its 100% clean electricity target. What’s worse, the newfound energy gap would almost certainly be filled by burning more gas.

The Union of Concerned Scientists—a group firmly opposed to the continued operation of DCPP—conducted modeling analysis that revealed California’s electricity sector would emit an extra 15.5 million metric tons (MMT) of global warming emissions through 2030 due to DCPP’s closure. Further, the natural gas increase would expose Californians to air pollution roughly equivalent to emissions from 1,890 diesel school buses operating over the next decade.

Growing support for Diablo Canyon drove Gov. Gavin Newsom to reconsider his objections and extract the nails from Diablo’s coffin, pushing to maintain the facility as an essential part of the state’s energy plan. Last September, California’s state legislature passed a bill that extended operations at Diablo Canyon up to 2030. Two months later, DCPP was awarded a $1.1 billion grant by the Department of Energy (DOE) to make necessary upgrades and maintenance, in a move that showed notable synergy between federal and state efforts to address climate change.

The NRC’s Role to Play

Last fall, DCPP’s owner, Pacific Gas & Electric (PG&E), filed a letter with the NRC requesting an exemption from a requirement that license renewal applications are submitted five years prior to license expiration. Now, the fate of Diablo Canyon rests with the NRC, which, next month, will render a decision on PG&E’s request. The agency’s judgment will determine whether DCPP is able to maintain its license while it undergoes the license renewal process, or whether the plant must cease operation while the NRC completes its review—thereby increasing the barriers for PG&E (and California) to meet its climate commitments, displacing hundreds of employees, and severely jeopardizing the state’s energy system and public health.

We’ve urged NRC staff to heed similar precedents and grant the exemption in the interest of climate, health, and good regulation. The consensus on this issue is glaring, even among parties opposed to operating DCPP: a denial of the exemption would be akin to pulling the rug out from under California’s energy system. For the NRC, an agency whose mandate and motto is “protecting people and the environment,” the stakes for both could not be more clear.

Nuclear Energy Is Essential for Decarbonization

The end of this decade will serve as the benchmark for measuring the success of the clean energy transition and the achievability of our decarbonization goals. States and utilities around the country will be re-developing their energy strategies to maximize the value of federal funding from the Infrastructure Investment and Jobs and Inflation Reduction Acts. U.S. states will need to build more nuclear plants to complete the transition to clean energy.

As this milestone draws near, it’s critical that we’re realistic about the value of nuclear energy as reliable clean electricity. California’s trajectory on DCPP is a lesson in how real-world constraints such as supply chains, transmission development, and permitting need to be addressed swiftly to support our energy investments. With so much at stake for the future of the energy transition, it can often be difficult to know where and when to start. For the NRC, the answers to those questions are simple: Right here, right now—by granting the exemption for Diablo Canyon and undertaking a prompt license review.

Stephen G. Burns served as the 16th chairman of the U.S. Nuclear Regulatory Commission from Jan. 1, 2015, through Jan. 23, 2017, and is a senior visiting fellow at Third Way. Ryan Norman is a senior policy analyst for Third Way’s Climate and Energy Program focused on federal policies for U.S. decarbonization and nuclear energy.